Various medical procedures, in particular, surgical procedures, involve the repair of diseased or damaged tissue by replacing the tissue with a graft. The graft may be natural, synthetic or a combination of the two. Examples of current procedures involving grafts are described below, along with certain short comings associated with each.
Coronary Artery Bypass
Coronary artery bypass grafting is a procedure used in the treatment of ischemic heart disease wherein the heart receives insufficient oxygen. Most often, ischemia is caused by atherosclerotic disease of the epicardial coronary arteries wherein the lumen of these vessels is reduced in size, reducing and/or limiting the flow of blood to the heart. In the bypass procedure, a section of vein, usually taken from the leg of the patient, is used to form a connection between the aorta and the coronary artery distal to the obstructive region, thus, restoring adequate blood flow.
While the operation is considered to be relatively safe, significant trauma is experienced by the patient in the harvesting of the vein which is used to effect the connection in the operation. Natural veins are currently preferred over synthetic grafts because it is very difficult to form a vessel suitable for use in bypass operations which remains unobstructed. The inner diameter of such veins is on the order of 6 mm, and synthetic grafts of this size are currently unacceptable because they are subject to occlusions due to collapse and clotting.
There is clearly a need for a graft having a small diameter lumen useable in bypass operations instead of a natural vein in order to avoid the trauma associated with harvesting the vein from the patient.
Repair of Severed Nerve Ganglia
When nerve ganglia are severed, as, for example, in an injury, a piece of the nerve is often destroyed in the process, leaving a severed nerve having two nerve endings which should be connected. It is sometimes possible to reconnect the severed nerve endings by stretching the ends and suturing them together. However, this technique is only effective if the nerve endings are separated by 3 mm or less. When the separation distance is greater than 3 mm, they cannot be successfully stretched to make up the separation distance. Instead, the ends are encouraged to grow together. However, muscle and other tissue near the injured nerves tends to interfere with the growth of the ganglia. It would be advantageous to provide a temporary graft which would encourage the growth of the nerve cells and prevent interference by nearby tissue.
Skin Grafts
Skin which is damaged by heat, abrasion, ulcerations or wounds is sometimes repairable by removing skin from one part of the body to serve as a graft on the injured part. However, this requires that the patient undergo the trauma of harvesting the graft, creating yet another region of the body which is subject to infection and which must be allowed to heal. Skin grafts which do not require harvesting of skin from another part of the body would provide significant improvement to the treatment of damaged skin tissue.
Hernia Operations
A hernia is the protrusion of a loop of an organ or tissue through an abnormal opening, for example, a protrusion of loops of the intestines through the abdominal wall. Current techniques for repair of a hernia involve invasive surgery to implant a graft to repair and strengthen the abnormal opening in the wall. Grafts currently used in this operation tend to be extremely flexible and are not, therefore, suitable for manipulation via less invasive laparoscopic techniques. Treatment of hernias would be improved significantly by the development of grafts which could be laparoscopically positioned and attached in order to eliminate the need for the trauma normally associated with the surgery.